1. Field of the Invention
This invention generally relates to motor vehicle sensor systems. More specifically, the invention relates to motor vehicle sensor systems having sensors that determine misalignment of a directional sensor.
2. Description of Related Art
In motor vehicle design, vehicle sensor systems are becoming increasingly important. Vehicles often include sensor systems used to sense the presence and distance of other vehicles traveling nearby, to alert the driver, or to automatically deploy certain safety and dynamic stability systems. Sensor systems may be configured to trigger vehicle safety systems or vehicle reaction systems, such as automatic braking or reduction of engine torque upon the occurrence of predetermined conditions. Such sensor systems may be used to provide a signal into a feedback control system. For example, a forward-sensing radar sensor may be part of a feedback control system that controls the speed of a vehicle based upon the distance of the vehicle traveling in front of it.
Other types of forward-looking sensors may use light or acoustic signals, or may use other forms of electromagnetic radiation, either actively (with an emitter) or passively (detection only). For the purposes of this description, a “forward-looking sensor” is any sensor oriented in a specific direction to detect conditions outside of the sensor. The “forward” is related to the sensor itself and not necessarily the forward direction of vehicle travel.
These types of vehicle forward-looking sensor systems must be very accurately aligned with respect to a geometric axis of a vehicle in order to properly sense the surrounding conditions that they are intended to measure. For example, the boresight of the sensor assembly might be required to be aligned with the direction of travel of the vehicle. If such a sensor assembly is not properly aligned, there must be compensation for misalignment in order to obtain a proper reading from the sensor assembly. Misalignment may result in mismeasurement of the desired surrounding circumstances. Such mismeasurement is undesirable because it may cause customer dissatisfaction and/or system performance concerns.
Various methods have been employed to determine sensor misalignment in the context of motor vehicles. For example, one known method of aligning a radar system is by using a second radar system to sense stationary objects along the side of the road. If the second radar senses that the objects are moving toward or away from the vehicle in a direction perpendicular to the direction of travel, it is evident that the first sensor assembly is misaligned. This method may be undesirable due to its complexity and costs.
Another known method of aligning a radar system is by aligning an optical axis with a light cone. This method may be undesirable because it may be time-consuming and costly to implement.
In view of the above, it is apparent that there exists a need for a system that is capable of efficiently determining whether a forward-looking sensor is misaligned.